High-speed search method for LSP quantizer using split VQ and fixed codebook of G.729 speech encoder

• US 20010010038A1
• Filed: 12/28/2000
• Published: 07/26/2001
• Est. Priority Date: 01/14/2000
• Status: Active Grant

• Current Assignee: CS Technology
• Original Assignee: CS Technology
• Inventors: Kang, Sang Won, Lee, Won Il, Son, Chang Yong, Shim, Min Kyu, Hong, Seong Hoon, Sung, Yoo Na
• Granted Patent: US 7,389,227 B2
• Time in Patent Office: Days
• US Class Current: 704/222
• CPC Class Codes: G10L 19/07 Line spectrum pair [LSP] vocoders
• CPC Class Codes: G10L 2019/0005 Multi-stage vector quantisation

Abstract

A high-speed search method in a speech encoder using an order character of LSP (Line Spectrum Pair) counts in a LSP count quantizer using SVQ (Split Vector Quantization) used in a low-speed transmission speech encoder, includes the steps of rearranging a codebook according to an element value of a reference row for determining a range of code vectors to be searched; and determining a search range by using an order character between a given target vector and an arranged code vector to obtain an optimal code vector.

The method gives effects of reducing computational complex required to search the codebook without signal distortion in quantizing the LSP counts of the speech encoder using SVQ manner, and reducing computational complex without loss of tone quality in G.729 fixed codebook search by performing candidate selection and search on the basis of the correlation value size of the pulse position index.

Claims

1. A high-speed search method in a speech encoder using an order character of LSP (Line Spectrum Pair) counts in a LSP count quantizer using SVQ (Split Vector Quantization) used in a low-speed transmission speech encoder, the high-speed search method comprising the steps of:

rearranging a codebook according to an element value of a reference row for determining a range of code vectors to be searched; and

determining a search range by using an order character between a given target vector and an arranged code vector to obtain an optimal code vector.

2. The high-speed search method as claimed in

claim 1

, wherein the rearranging step comprises the steps of:

selecting the reference row in each codebook by using a plurality of voice data, and then determining an optimal arrangement position (Nm) in which an average search range is minimized; and

replacing the codebook with a new codebook in which a number (Lm) of code vectors in the codebook are arranged in a descending order according to an element value of the selected reference row.

3. The high-speed search method as claimed in

claim 1

, wherein the code vector-obtaining step comprises the step of:

determining the search range by forward and backward comparison of the element value of the reference row in the arranged codebook and element values of rows before and after the target vector; and

obtaining an error criterion (E_1,m) having high computational complexity by using the below Equation 2 only within the determined search range.

4. The high-speed search method as claimed in

claim 3

, wherein the search range is an average number with which an element value of the n^th row in the arranged codebook and element values in the n+1^th and n−

1^th positions of the target vector satisfy the order character.

5. A high-speed search method in the G.729 fixed codebook with decreased computational complexity without loss of tone quality, the high-speed search method comprising the steps of:

arranging position indexes of tracts (t₀, t₁, t₂) in a descending order according to a correlation level (d′

(n));

determining a range to search a tract (t3) according to the indexes arranged in a descending order; and

canceling the detecting and searching processes for indexes which has low probability.

6. The high-speed search method in the G.729 fixed codebook as claimed in

claim 5

, wherein the arranging step comprises the step of:

comparing correlation vectors of all of the pulse position indexes in each track to arranging the position indexes in a descending order.

7. The high-speed search method in the G.729 fixed codebook as claimed in

claim 5

, wherein the search range-determining step comprises the steps of:

adding correlation values of each pulse position index for the pulse position index combination of the tracks (t₀, t₁, t₂); and

comparing the added result with a threshold (Cth) determined before the search of the fixed codebook to search track (t3) using an added result more than the threshold.

8. The high-speed search method in the G.729 fixed codebook as claimed in

claim 5

, wherein the canceling step comprises the step of:

canceling the searching process for the range where the added result is less than the threshold.